The present invention relates generally to packaging systems that deform a web of flexible material into product-holding cavities and, more particularly, to a belt-driven clamping arrangement that advances the web of flexible material through the various stations of a packaging system.
Conventional packaging machines that deform a web of flexible material into product-holding cavities, such as described in U.S. Pat. No. 4,915,283, have a clamping arrangement in the form of a pair of spaced apart clip chains that grip the edges of the web and advance the web through the machine. In this regard, the clips or clamps used to grip and release the web of flexible material are mounted at predefined positions along the length of the chain. When the chain is taut, the position of the clamps can be controlled; however, over time, the chain can wear and become loose and, thus, the position of the clamps can become difficult to control. In this regard, periodic shut-downs of the packaging system are required for maintenance of the chain.
In addition, prior art packaging machines utilizing a chain-type clamping arrangement involve the use of a drive motor that rotates a drive shaft, and a pair of drive sprockets that are mounted to the drive shave. Each drive sprocket is engaged with one of the clip chains. The drive shaft extends across the width of the packaging machine, and is operable to synchronously drive the drive sprockets so as to move the clip chains together. With this construction, the components of the machine must be arranged so as to provide clearance for the drive shaft. In addition, in the event the chains wear unevenly, this arrangement can result in the opposite edges of the web material being advanced at slightly different rates of speed through the machine, which can cause skewing and wrinkling of the web material.